Originally Posted by jlemon

2. In 1973, which airline and aircraft provided nonstop service between Los Angeles and San Juan, PR?

Delta with a DC-8. The aircraft may have been a DC-8 Super 60 series. Or it may have been a good old fashioned DC-8 series 50.
Back in 1973, Delta was ready when you were with a D8F departing LAX at 9:40pm, arriving San Juan at 7:33am the next morning. A full dinner was served enroute.

12. This airline operated Martin 404s between Miami and Key West, Florida.

Air Florida. I think they may have been also operating B737-200 flights between MIA and EYW in addition to their Martin 404 service at this time.
Right on! Air Florida offered travelers on the MIA-EYW RUN a colorful and eclectic choice between a 737-200 or a Martin 404. Pro Air also provided a nightly DC-3 service departing MIA at 7:00pm.

14. While two other airlines operated DC-9s on the 765 mile route between Houston and Mexico City, these two airlines offered 747 service.

Air France and Pan Am. The AF routing was CDG-IAH-MEX and I believe some of these Air France flights were operated with a B747 Combi.
Si, Señor! On Monday, Wednesday and Thursday Air France operated a 747 Combi on this run, replacing it with a standard 747 on Saturdays. I had the good fortune to occupy a First Class seat aboard Air France's 5:10pm departure out of Houston one spring evening in 1980. An upgrade to First Class cost just $26.00 more back then. I remember a delicious starter of Pâté de Foie Gras and some type of canard (or was it poulet?)for the main course. Unfortunately, the upper deck had by then been changed over to an all economy class configuration. Pan Am was the other 747 operator on this route, additionally offering seats aboard a daily L-1011-500 and a 727-200.

15. Which two airlines provided the only nonstop jet service between Los Angeles and Fresno?

Three airlines come to mind: Air California, PSA and United. But, of course, we are looking for only two carriers here. So I'll go with Air California and PSA.
Having flown this route twice aboard United DC-8s back in the 1970s, the latest flight having come aboard a DC-8-61 in 1977, I would have picked United as one of the carriers. I would have been wrong. Way to break it down, Mr. Lemon. OC and PS are correct!

18. This airline operated daily nonstop DC-3 service between Tampa and Naples, Florida.

Provincetown-Boston Airlines (PBA).
Correct! As their name implies, PBA's principal route was between Provincetown and Boston. In 1958 a merger with Florida's Naples Airlines allowed for expansion into Florida though PBA never provided service between the Northeast and Florida. My first DC-3 flight came aboard a PBA flight between Miami and Naples in 1986.

20. Everyone knows that Northwest operated lots of flights from Minneapolis to all three New York airports. Only one other airline offered nonstop flights into any of the three New York airports. That airport was Newark. Name the airline.

US Air.
Correct!

21. This airline offered once weekly nonstop service between St. Kitts, Leeward Islands and New York JFK. Name the airline and the aircraft used on this route.

American Airlines with B707 service.
Alas, it was a different airline...

22. Name the four airlines that provided nonstop jet service between Denver and Phoenix.

Continental, Frontier, United and Western
You da man, jlemon! Excellent recall!

23. This airline offered nonstop Fokker F28 service between Greensboro and Raleigh, NC.

Well, I wanted to say Piedmont. But I think it was actually Altair.
This sure seems like a Piedmont route, and indeed it is but then I don't believe PI operated F28s until its purchase of Empire Airlines in 1985. Altair it is. Good call!

24. This airline offered the only service between New York’s three airports and Utica, New York. Name the airline and the jet that it flew.

Empire with the Fokker F28.
Nuff said. You are correct, sir.

25. These two airlines operated daily nonstop Convair 580 service between Burbank and Lake Tahoe, CA.

Well, I know that Aspen was one of the carriers but I'm unsure of the other one....so I'll go with Sierra Pacific as the other CV580 operator BUR-TVL.
Aspen was indeed one of the airlines. The other was Cal Sierra, a start-up commuter carrier based out of San Diego operating TVL-BUR-SAN service. Aspen offered nonstop TVL-LAX flights in addition to one stop direct flights via BUR, all operated with its colorful Convair 580s.